This invention relates to analysis of a sample. More particularly, the invention relates to the analysis of a sample obtained for the diagnosis of a disease. Still more particularly, the invention relates to analysis of a sample by means of antigen/antibody mediated agglutination reactions.
The use of antigen/antibody reactions to prepare an analyte for diagnosis is well known and is commonly used with such analytical procedures as radio immunoassay and enzyme immunoassay. Both of these procedures use antigen/antibody reactions to bind an analyte to a detectable marker. The amount of marker that is bound to the analyte directly correlates with the amount of analyte in the sample and becomes an index of the presence or extent of a disease. For example, a tumor. Problems associated with these methods include the preparation time requirement of the analyte, and the safe disposal of the analyte.
A proposed counting immunoassay method uses antigen/antibody reactions in the preparation of the analyte. These antigen/antibody reactions detect by aggregation even small percentages of the analyte of interest in the sample with improved sensitivity and decreased sample preparation time.
In this method, a sample containing the antigen to be measured is mixed with insoluble carriers that are sensitized with the multivalent specific antibody for the subject antigen. These carriers are, for example, made up of micron sized latex particles. The reaction between the antigens in the sample and the antibodies bound to the latex particles causes the reacted carriers to aggregate. Measuring the number of total carriers, in comparison with the number and degree of aggregation of carriers, determines the concentration of the antigen in the sample. A major problem of this method is that the analyte may be contaminated with spurious particles, such as chylous particles, cell fragments or the like, that decrease the accuracy of the measurement. These spurious particles cannot be differentiated if they fall within the size range of the non-aggregated and aggregated insoluble carriers. The presence of the spurious particles greatly reduces the reliability and accuracy of the measurements. It is possible to eliminate the spurious particles from the sample prior to measurement, but this requires a substantial amount of preprocessing.